1. Field of the Invention
The present invention relates generally to an apparatus and method for transmitting voice/data frames in a mobile communication system supporting an ALL-IP network that transmits both packet data and circuit data using an Internet protocol (IP), and in particular, to an apparatus and method for removing a header from an ALL-IP-based voice/data transmission frame.
2. Description of the Related Art
An IMT-2000 (International Mobile Telecommunication-2000) network supports both a packet network and a circuit network. Recently, in order to more effectively perform packet transmission in the IMT-2000 network supporting both the packet network and the circuit network, attempts have been made to integrate the networks into an IP network, called an ALL-IP network. The integration of the existing networks into the ALL-IP network has been conducted by a future mobile communication standardization organization including the 3GPP (3rd Generation Partnership Project), the UMTS (Universal Mobile Telecommunications System) standardization organization. The ALL-IP network has an open-type data network structure, so it can effectively introduce various services that will become available in the future, especially IP-based services. In addition, the ALL-IP network, as can be inferred from the term, has a function of transmitting circuit data, i.e., voice through packetization. Therefore, for voice transmission, the ALL-IP network converts a voice into voice data and transmits the converted voice data in a frame unit (hereinafter, referred to as “voice frame”). The voice frame includes an IP header so that the voice data can be properly transmitted to the IP network.
FIG. 1 illustrates a structure of a UMTS system having an IP network. Referring to FIG. 1, UMTS system consists of a Node B (111-2), a radio network controller (RNC) 120 controlling the Node B, a co-network (CN) 140, a serving GPRS (general packet radio service) support node (SGSN) 130, a gateway GPRS support node (GGSN) 150, and a mobile terminal (MT) 101 is connected to an IP network 160 through a Node B 111-2, an RNC (Radio Network Controller) 120, an SGSN (Serving GPRS (General Packet Radio Service) Support Node) 130, and a GGSN (Gateway GPRS Support Node) 150. Here, the mobile terminal 101 may include a mobile phone or a personal computer (PC) connected to the mobile phone. During voice and data transmission, the mobile terminal 101 packetizes voice and data according to the Internet protocol (IP), and then transmits the packetized voice and data to the IP network 160 through the above elements.
The mobile terminal 101 converts voice input by a user into voice data, and constructs a voice frame using the converted voice data. The mobile terminal 101 generates a transmission frame by adding headers to the voice frame, and transmits the generated transmission frame to the Node B 111. The structure and operation of the mobile terminal 101 and the Node B 111 will be described in detail with reference to FIG. 2.
Referring to FIG. 2, a voice frame generator 203 converts voice input by the user into voice data, and constructs voice frames using the converted voice data. A signaling generator 201 receives information on an IP address or telephone number input by the user, and provides a protocol stack 205 with a header generation signal based on the received information. The protocol stack 205 generates header information according to a real time protocol (RTP), a user datagram protocol (UDP), and Internet protocol (IP), in response to the header generation signal. The headers generated by the protocol stack 205 are added to the head of the voice frame generated by the voice frame generator 203, and then transmitted to the Node B 111 through a channel allocated by a physical layer 207. Reference numeral 221 represents the voice frame generated by the voice frame generator 203, and reference numeral 223 represents the voice frame to which an RTP header ‘b’ is added in an RTP layer. Further, reference numeral 225 represents the RTP header-added voice frame output from the RTP layer, to which a UDP header ‘c’ is added in a UDP layer, and reference numeral 227 represents the RTP/UDP header-added voice frame output from the UDP layer, to which an IP header ‘d’ is added in an IP layer. As represented by reference numeral 227, the transmission frame is constructed by adding the RTP header ‘b’, the UDP header ‘c’ and the IP header ‘d’ to the voice frame, and the transmission frame is transmitted to the Node B 111 through the physical layer 207.
The Node B 111 receives the transmission frame transmitted by the mobile terminal 101 through a physical layer 211. A frame processor 213 detects (extracts) headers from the transmission frame received through the physical layer 211, and processes the voice frame according to the detected header information.
For example, an existing UMTS AMR (Adaptive Multi Rate) codec inserts a 40-byte header in a 30-byte voice frame in order to transmit a transmission frame in the ALL-IP network. FIG. 3 illustrates a structure of the transmission frame. For example, if a voice frame handled by the AMR codec is 15-32 bytes, then a header of a total of 40 bytes including a 12-byte RTP header, an 8-byte UDP header and a 20-byte IP header is added to the head of the voice frame. Further, an additional header may be optionally added to the voice frame. As a result, the actual size of the voice frame among the transmission frames transmitted over a radio link becomes less than 50% of the whole traffic.
As described above, in the mobile communication system employing the ALL-IP network, during data transmission, the size of the header is larger than the number of bytes of the actual transmission voice data, bringing about a waste of radio resources.